Vapor type printers have been proposed for applications requiring impression of video and/or television images on paper or the like. Such color video printers include a printer head which ultimately converts a solid dye into a vapor for printing on a substrate. Because this printer does not use an ink ribbon or a heat-sensitive head, it uses less electric power and is smaller in size.
In copending U.S. patent application Ser. No. 08/183836 which was filed on Jan. 21, 1994, a color video printer having a printer head capable of converting a solid dye and transferring into a substrate as a gas is disclosed. The above application is owned by the assignee of the present invention and is hereby incorporated herein by reference.
The color video printer head disclosed in U.S. patent application Ser. No. 08/183836 is explained with reference to FIGS. 12 and 13 as follows. FIG. 12 shows a perspective view of an example of the color video printer. FIG. 13 shows a cross-sectional view of a printer head assembly included in FIG. 12.
The color video printer 30A has an outer case 31A, a chassis 32A, a cassette 33A, a planar base 34A, a head assembly 35, a feed roller 36, a pressure driven roller 37, an electric source 38, a feed motor 39, a head driving circuit substrate 40 and a flexible wire harness 41.
The outer case 31A is a cubic box covering the whole of the color video printer 30A and has a discharge slot 31a on the right side thereof. The chassis 32A is an inside case for dividing the inside of the outer case 31A to a space for the cassette 33A and a space for other elements.
The cassette 33A holds a substrate 43 for printing such as a paper (referred to as "paper" hereinafter) and is provided in the left space of the chassis 32A. The right side of the cassette 33A is an opening. The paper 43 is pushed out from the opening one by one.
The planar base 34A is provided on the right space of the chassis 32A. The paper 43 is held between the planar base 34A and the head assembly 35.
The head assembly 35 is provided on the planar base 34A. The head assembly 35 is a printer head for printing to the paper 43 held between the planar base 34A and the head assembly 35. The head assembly 35 is pressed against the planar base 34A by springs 42a and 42b with a small load, about 50 g, for example.
The head assembly 35 has a solid dye tank 44 on the upper side thereof. The solid dye tank 44 includes a tank for solid powdered yellow dye 45Y, a tank for solid powdered magenta dye 45M and a tank for solid powdered cyan dye 45C (collectively referred to hereinafter as "powdered dye 45").
In the present invention, the powdered dye 45 may include any number of dye types including solidified disperse dye, liquefied disperse dye, sublimation disperse dye, or sublimation dye or disperse dye. In the preferred embodiment, the powdered dye 45 is defined as dye having a vapor pressure which is 0.01 pascal or more in a temperature range of 25.degree. C. to a decomposition temperature. Further when dye molecules are associated with an average association value n in gas phase, the dye is defined as dye having a value equal to the vapor pressure of the dye divided by the average association value n, which is 0.01 pascal or more in a temperature range of 25.degree. C. to a decomposition temperature. Solid dyes on the market corresponding with this definition is, for example, HSR-2031, ESC-155 or ESC-655.
The feed roller 36 and the pressure driven roller 37 are rotated in a reverse direction to each other by the feed motor 39. The paper 43 printed by the head assembly 35 is discharged outside from the discharge slot 31a being held by a small pressure of the feed roller 36 and the pressure driven roller 37.
The head driving circuit substrate 40 has a circuit for operating the head assembly 35. A terminal of the circuit is connected to the control circuit of the head assembly 35 through the flexible wire harness 41.
Referring to FIG. 13, the head assembly 35 has a solid dye tank 44 for accommodating powdered dye 45, a plurality of liquefied dye supplying passages 46 connected to the solid dye tank 44 and a vaporizer portion 47 connected to an exit of each liquefied dye supplying passage 46.
The liquefied dye supplying passage 46, the solid dye tank 44 and the vaporizer portion 47 are provided in a transparent plastic head base 49 through an insulating layer 48 formed by an insulating material such as polyamide.
A ventilator 44a is provided at an upper side of the solid dye tank 44 penetrating the insulating layer 48 and the head base 49. The diameter of the ventilator 44a is smaller than the diameter of the powdered dye 45. The ventilator 44a is used for sending out the powdered dye 45 to the liquefied dye supplying passage 46 smoothly.
The powdered dye 45 is introduced from the solid dye tank 44 to the liquefied dye supplying passage 46. The powdered dye 45 is liquefied and then is provided to the vaporized portion 47 by capillarity. The lower wall of the liquefied dye supplying passage 46 is made of a protecting layer 50 having a high durability.
A heater 51 made of an electric resistance element is provided at a lower surface of the insulating layer 48 which is the upper wall of the liquefied dye supplying passage 46. The heater 51 heats the powdered dye 45 up to the melting point so as to liquefy the powdered dye 45.
An entrance of the vaporizer portion 47 is joined with an exit of the liquefied dye supplying passage 46. A heating portion 52 heats the liquefied dye so that the liquefied dye is vaporized thereby. The heating portion 52 may include a laser source and a light-heat conversion layer.
A protection layer 50 is provided under the vaporizer portion 47 and beneath the heater 51.
A vapor hole 53 for getting out the vaporized dye is provided at the protection layer 50 located under the vaporizer portion 47.
Steps for printing by the color video printer 30A is explained as follows. At first, some pieces of paper 43 are put into the cassette 33A as shown in FIG. 12. A layer for accepting dye 43a is provided on the surface of the paper 43 as shown in FIG. 13. When a printing starts, the paper 43 is held between the head assembly 35 and the planar base 34A one by one by sufficient pressure to maintain contact between the head assembly 35 and the paper 43. At that time, the layer for accepting dye 43a faces the vapor pole 53.
On the other hand, the powdered dye 45 accommodated in the solid dye tank 44 is sent to the liquefied dye supplying passage 46 and heated to the melting point of the powdered dye 45 so that the powdered dye 45 becomes liquefied. The liquefied dye 45A runs inside of the liquefied dye supplying passage 46 by capillarity and is supplied to the vaporizer portion 47.
When the paper 43 is held between the feed roller 36 and the pressure driven roller 37, a print signal for a line of a color is sent to the circuit for operating the head assembly 35 from the head driving circuit substrate. The heating portion 52 of the head assembly 35 heats the liquefied dye 45A so as to vaporize the liquefied dye 45A accommodated in the portion 47.
The vaporized dye 47A goes through the vapor port 53 and is transferred to the layer for accepting dye 43a provided on the surface of the paper 43. The above-described printing steps are repeated three times for three colors (Y, M, C) so as to make one line of the color print.
The vaporized dye 47A transferred to the layer for accepting dye 43a is heated by the heat conducting through the protection layer 50 so that the vaporized dye 47A is fixed in the layer for accepting dye 43a.